Photochromic cellulosic paper, synthetic paper and regenerated cellulose



United States Patent Oil 3,314,795 PHOTOCHROMIC CELLULOSIC PAPER, SYN- THETIC PAPER AND REGENERATED CEL- LULOSE George Henry Dorion, New Canaan, and Kay Oesterle oefller, Norwallr, Conn, assignors to American Cyan- 1a rlnid Company, Stamford, Conn, a corporation of aine N Drawing. Filed Mar. 1, 1963, Ser. No. 262,254 13 Claims. (CI. 9690) This invention relates to photochromic cellulosic paper, photochromic synthetic paper and photochromic re- More particularly, this cellulose film containing uniformly distributed throughout its mass, a photochromic material. Still more particularly, this invention relates to cellulosic paper, syncontaining unia photochromic the solid state.

The production of photochromic paper per se is not new in the art. Berman, in US. Patent No. 2,953,454,

paper wherein the paper is coated with minute, liquidcontaining capsules having light-translucent walls, said liquid having dissolved therein a photochromic material. The method disclosed by Herman, however, is relatively lest its usefulness will be destroyed by rupture of the capsules upon the slightest contact.

We have found attractive characteristics of its color changing ability. Additionally, we have found that photochromic materials which function only in solution cannot be added to the cellulosic paper, synthetic paper or regenerated cellulose without losing their ability to function photochromically.

It is an object of the instant invention to present photochromic cellulosic paper, photochromic synthetic paper and photochromic regenerated cellulose.

It is a further object of the instant invention to present cellulosic paper, synthetic paper and regenerated cellulose films having uniformly dispersed throughout their masses, a photochromic material.

It is still a further object of the instant invention to present cellulosic or synthetic paper and regenerated cellulose, containing, uniformly dispersed throughout their masses, a photochromic compound which is photochromic in the solid state.

These and further objects of the instant invention will 3,314,795 Patented Apr. 18, 1967 ice become more apparent to one skilled in the art upon reading the more detailed description set forth hereinbelow.

PHOTOCHROM-ISM Molecules or complexes which undergo reversible photo-induced color changes are termed photochromic sys- That is to say, in the absence of activating radiation, the system has a single stable electronic configuration with a characteristic absorption spectrum. When the system is contacted with ultraviolet irradiation the absorption spectrum for the system changes drastically, but when the irradiation source, is removed, the system reverts individual system, in many inorganic systems it can be related to one of two possible reaction schemes.

The first process is the alteration of the force field (A) Absorption of incident radiation According to the quantum theory, each absorbed quantum creates one activated molecule and only absorbed radiation can produce a chemical change. Variables which control the number of photons absorbed include the concentration and extinction coeificient of the photochrome, the screening coefiicients of other components of the system, and the wavelengths of the incident radiation.

(B) Quantum yield (C) The reverse reaction In both the forward and reverse reactions, the concentration of the colored form is dependent on the intensity of the radiation, the kinetics of the reverse reactions, and temperature of the reactions. The kinetics for the reverse reaction will normally be controlling, however some reverse reactions are thermally sensitive and are accelerated by irradiation or heating.

By the terms photochromic compound, photochromic substance as used in the instant disclosure, is meant compounds, substances or materials which change their transmission or reflectance upon being subjected to ultraviolet or visible irradiation and subsequently revert to their original color state upon subjection thereof to a different wavelength or radiation, or removal of the initial ultraviolet source.

The ability of various materials to change color and to then revert back to their original color is not a new phenomena. In fact, such compounds have been widely FO, (31 203, C110,

THE PHOTOCHROMIC ADDITIVES The photochromic additives which are incorporated into oellulosic paper, synthetic paper or regenerated cellulose to form the novel products of the present invention are not critical in regard to the specific chemical class of compounds used, except that the compounds must be photochromic in the solid state. That is to say, compounds which are solid but only exhibit photochromic properties in solution cannot be employed to form the products which constitute the subject matter of the present invention. Only those materials which are solid and which function photochromically, as such, are contemplated herein. However, a material which functions photochromically both in the solid state and in solution falls within the scope of the present invention. By solid as used in the present specification, is meant those compounds which are solid, as opposed to liquid, at room temperature and reversibly change color at that temperature when contacted with ultraviolet light. Examples of compounds which fall into this category and therefore may be used to form the novel products of the present invention are set out more fully hereinbelow.

One class of photochromic materials which are useful in producing the products of the present invention are composed of inorganic metal oxides. The materials generally consist of a primary or host inorganic metal oxide doped with a lesser or contaminating amount of another guest inorganic metal oxide. The materials which are contemplated as useful in the novel compositions of our invention are the following: TiO doped with F8 NiO, MnO or Mn O Nb O doped F6203, FCO, C1203, C110, V205, M1102 Or M11205; A1 0 doped with Cr O or V 0 ZnO doped with CuO or V 0 SnO doped with CuO; or ZrO doped with CuO or NiO. In regard to the TiO the rutile form of the compound is sufficient, however, the anatase form containing at least 5% of the rutile material is preferred. These photochromic materials contain from about 0.0 1 to 5.0 mole percent of the doping guest oxide, preferably 0.1 to 2.0 mole percent, based on the number of moles of the host oxide.

These doped oxides are well known in the art and generally may be prepared by any applicable method. Various methods which may be used include those set out in the following articles. Williamson, Nature (London), 140, 238 (1937); McTa-ggert et al., J. Appl. Chem, 5, 643 (1955); Frydryck, Doctoral Thesis, Free University of Berlin (1961), and the method set forth hereinbelow. By the word doped or doping as used herein in regard to all the oxides, is meant the result obtained from or the method of forming the photochromic oxides as set forth in the above-enumerated articles.

A second class of photochromic materials that may be employed in forming the products of the present invention comprises materials composed of TiO with a combination of two doping (guest) metal oxides. These materials composed of guest oxides, in admixture with TiO exhibit a more pronounced effect in the color intensity of the products than either doping metal (guest) oxide used alone. For example, TiO doped with Fe o, or FeO and NiO or TiO doped with Fe O or PeO and CuO, result in a more intense color change than TiO doped with Fe O FeO, NiO or CuO, alone. That is to say, a synergistic effect is observed wherein the results 4 obtained utilizing a mixture of guest oxides is better than that obtained from either guest oxide alone or the mere additive results of both together. Here, again, the rutile form of the host compound is satisfactory, but the anatase form containing at least 5% of the rutile material is preferred. When a combination of the difierent doping oxides are used, amounts ranging from :1 to 10:1, preferably 25:1 to 5:1, of the iron oxide to the nickel or copper oxide are satisfactory, the total amount of the mixed oxides still however, being within the range (in mole percent) specified above.

These materials composed of host and guest oxides, either, as such, or with combinations or doping guest oxides, may be prepared, among other methods, by slurrying a solution of the doping metal oxide salt, the guest metal oxide itself, or mixtures thereof, with the host metal oxide. The slurry is evaporated and ground, then calcined at a temperature between 400 and 1100 C. to give the active composition. In the case of TiO the host crystalline compound desired can be previously prepared, or starting the preparation with anatase, the desired final proportion of rutile can be controlled by the length of time the admixture is calcined above the phase transition temperature (ca. 800 C.). The final acti ve photochromic materials are not merely mechanical or physical blends, but are crystalline materials consisting of a host material matrix wherein is contained sub stitutionally or interstitial'ly, the doping guest metal oxide.

A third class of photochromic inorganic oxide materials which may be used to form the products of the present invention are T iO reacted with M00 or W0 These materials are produced in mole ratios of about 1 to 15 mole percent of TiO to about 25 to 1 mole percent of M00 or W0 The preferred mole ratios range from about 1:4 to about 12:1, respectively. The TiO component may be in either the rutile, anatase, or mixed phase form, and in place of T iO other metal oxide components may be used, such as, for example, ZnO, ZrO SnO and GeO in the same mole ratio given above for TiO These two phase materials constituting the third class of photochromic materials are prepared as described and claimed in copending application, Serial No. 239,159, filed November 21, 1962. In a typical procedure, the materials are prepared by dissolving the M00 or W03 in an aqueous basic solution and adding to this solution an acidified aqueous slurry or solution of the primary metal oxide component. After heating at up to 100 C. for several hours or longer, the desired active material is formed in a very high yield, separated from the solvent, washed free of acid, and dried.

superficially taken, it would appear that the third class of materials are merely mechanical or physical mixtures of the two oxide components. However, these latter chemically prepared coprecipitated materials are of eX- tremely greater photo-sensitivity in comparison to a mixture of their individual metal oxides. Additionally, X- ray evidence clearly indicates that the crystalline matrix of the M00 or the W0 has been completely altered. Although not wishing to be bound by any particular theory, it is possible that this phenomena can be explained as follows. Since the photochromic color in these compounds is deep blue, the most likely theoretical alternative as to the nature of this photochromic reaction is that a net electron delocalization to M0 or W takes place either by an interor intra-phase photoinitiated electron transfer from the second component of the active material.

Further examples of solid state photochromic additives which may be used to form the novel products of the present invention include:

(1) 2,3-diphenyl-1-indenone oxide (2) p-bromo-N- 5 -bromosalicylidene) aniline (3 N-( S-bromosalicylidene) -1-naphthylamine THE CELLULOSIC PAPER BASE According to the present invention, any cellulosic paper material may be used to form the photochromic products of the present invention. The cellulosic paper may be made from all types of fiber stocks, including those of poor quality, such as oak, poplar, and yellow birch, and those of extremely short fiber length, as well as those of long fiber length and of good quality derivation, such as from spruce and hemlock. A wide variety of fibrous cellulosic material used in the preparation of paper, board, molded resin fillers, and the like may be used, such as kraft pulp, rag pulp, soda, sulfate, ground-wood, sulfite pulp and alpha pulp. Similarly, other forms of paper-forming fibrous cellulose such as cotton linters, and the like may be employed. These materials may be used alone or in admixture with fibers from other sources, such as jute, hemp, sisal, strings, chopped canvas, and other material, either cellulosic or non-cellulosic.

It is further stressed that the cellulosic base paper may also be obtained from bleached or unbleached kraft, bleached or unbleached sulfite, or bleached or unbleached semi-chemical pulps. In addition, the paper may be made from mixtures of cellulosic paper-forming pulps with up to and preferably containing 1 to 5% of other fibers, such as glass fibers or a minor amount of any of the synthetic fibers mentioned hereinbelow.

For most purposes it is preferred that the starting cellulosic paper be unsized and generally free of added resins. However, for some purposes, it may be desirable to employ as the starting paper base sheet, a porous, high wet strength, pap-er such as may be obtained by incorporation into the paper base sheet 0.5 to 5% by weight, based on the weight of the fibers, of a thermosetting aminoplast resin, such as a urea-formaldehyde resin, a melamine-formaldehyde resin or methylolated ureido polymers, such as those obtained by the reaction of formaldehyde with polymers and copolymers of N-vinyl-oxyethy1-N,N'-ethyleneurea. Such wet strength cellulosic papers are obtained in the conventional way by the use of one of the resins just cited applied to the pulp suspensions followed by sheeting and baking at temperatures of 210 to 400 F. for periods of about one-half or an hour to five or ten minutes, respectively.

The method of making the cellulosic paper base is not critical and any paper-making process may be employed to form the paper bases used in the present invention. In the normal manufacture of paper, for example, cellulosic fibers such as those derived from wood pulp are beaten in water to disperse the fibers therein and to reduce them to a length and fineness suitable for use in papermaking. During the beating operation the cellulosic fibers fibrillate, the fibrillation manifesting itself by a fraying or shredding of the surfaces and ends of the fibers to produce minute tendrils or fibrils which serve to interlock the fibers together when they are deposited on the forming screen of a paper-making machine to make a sheet therefrom and dried. The interlocking of these fibrils projecting from the deposited fibers imparts coherency and strength to the paper. In other words, the strength in the paper is attained through the interlocking of large numbers of fiber branches or fibrils during sheet formation.

The photochromic material may be added to the cellulosic paper anytime during the production thereof or even after the paper has been sheeted. Therefore, it is within the scope of the present invention, to prepare a beater pulp of papermaking cellulose fibers of any convenient consistency, for example, between about u.5% to 5%. To this can be added any of the photochromic materials, described hereinabove. The suspension is agitated gently to distribute the emulsion particles uniformly therethrough and the aqueous suspension of fibers is then sheeted, preferably at a pH between 4.5 and 6, to form a wet waterlaid web containing the photochromic additive. The web is then dried on steamheated rolls, in accordance with conventional practice.

More specifically, in mills where various pigments are added at the beater, the photochromic material may be added therewith or at any point more than about one minute from the wire. In such mills the photochromic material may be added at any time but sulficiently far from the wire to permit deposition of the added photochromic composition in the fibers before the sheeting step begins.

In mills where the paper pulp suspension is given heavy refining, the photochromic material may be added to the beater, to the refiner effiuent or to the screen effiuent sulficiently ahead of the wire so that deposition becomes substantially complete before the sheeting step.

Thus, the application of the photochromic material may be easily adapted to most types of paper or mill conditions. Therefore, the photochromic material may be added to the paper pulp prior to sheet formation or may be applied to the sheet at a convenient point after sheet formation, even at the size press or calendar stacks, for example.

The paper obtained consists essentially of cellulose fiber having the photochromic material uniformly dispersed throughout its mass. The paper changes color upon contact with ultraviolet light and reverts to its original color upon removal of the light.

If the photochromic material is to be incorporated into a sheet of pre-formed cellulosic paper, it is only necessary to first wet the sheet on a screen, for example, and contact the wet web with the photochromic material, preferably for a period of time sufficient to enable substantially complete, thorough and uniform incorporation of the material into the paper fibers. The paper sheet is then dried to produce the desired photochromic cellulosic paper sheet.

THE SYNTHETIC PAPER BASE As mentioned hereinabove, it is also within the scope of the present invention to utilize fibrous or nonfibrous synthetic paper bases formed from synthetic paperforming polymers to produce the novel products of the present invention. In this regard, such materials as nylon and related polyamide polymers, polyethylene glycol terephthalate, and related polyester resins, polymers of acrylonitrile, such as copolymers containing at least 75%, by weight, of acrylonitrile with other comonomers such as vinyl acetate, vinyl chlorode, vinyl pyridine, and esters of acrylic or methacrylic acid may be employed in the present invention.

By the term synthetic paper, as used herein and throughout the instant specification is meant, those paper sheets produced from synthetic polymeric materials such as those set forth hereinabove, more specific examples of which are shown in e.g., US. Patent No. 2,810,646, along with methods for the production thereof, which patent is hereby incorporated into the instant disclosure by refer ence.

It can therefore be seen that synthetic paper comprising randomly intermingled discontinuous fibers which are at least in part composed of highly fibrillated, synthetic, non-cellulosic fibers of paper-making length may be used to form the novel products of the present invention. More particularly, synthetic paper comprising randomly intermingled discontinuous fibers which are at least in part composed of fibrillated wet-spun thermoplastic products of a polymerized mass of polymerized acrylonitrile may be used.

asbestos As in regard to the cellulosic paper bases, the photochromic materials which are added to the synthetic paper base, may be incorporated therein at any time during the manufacture of the synthetic paper sheet. Any method may be used to produce these synthetic sheets including, for example, the so-called hot method wherein a thermoplastic organic polymer is melted and extruded through spinnerettes into cooler air. A filament is formed when the polymer has cooled below its melting point. The photochromic material may conveniently be added, therefore, to the polymer at such times as when the polymer is melted or before.

A second method used to produce the synthetic paper bases useful in the production of the products of the present invention is the air dry method. In this method a polymer is dissolved in a suitable volatile solvent and the solution is again extruded through spinnerettes into air. A filament develops upon volatilization of the solvent. It can readily be seen that in this process the photochromic material may be added to the solution of the polymer or anytime before extrusion.

The wet spinning spinnerettes into a liquid in which the solvent dissolves but in which the polymer is insoluble. A filament develops when the solvent is leached from the polymer by the body of liquid into which the dissolved polymer is extruded. Here again the photochromic material may be a process comprising three basic steps.

First, the filament of convenient length and denier are refined in aqueous suspension until they have fibrillated and formed felting properties.

Second, the fibrillated filaments, alone or with other felting fibers, in water, are sheeted to form a water-laid Web.

Third, the web is heated to dry the same and to develop the bonding properties developed by step one.

Conveniently, and perhaps preferably, the photochromic material, if not added during the filament production, may be added during steps one or two of the sheet making process.

The refining step is performed in the same manner disclosed above in regard to the cellulosic papermaking process. That is, the filaments are beaten by ordinary methods, i.e. with Niagara and Hollander heaters, Hydro- The only ditnculty which arises in the addition of the photochromic material at this stage exists the danger that the material D It is for this reason .that the photochromic material is preferably added at step two, i.e. the web-forming.

In the web formation step, the fibrillated filaments are sheeted to form a web by the same procedures employed in cellulosic paper-making methods. The web may have any desired caliper so as to result in the formation of a tissue, a paper, a paper board or a building board as is known in the art, and may be subjected to suction to facilitate drying and may be passed through dandy rolls, calendar rolls and the like in the same manner as cellulosic webs.

Again, as in regard to the cellulosic paper bases, various other materials maybe added ess, such as, for example, cellulosic fibers, glass fibers, fibers, silk fibers and other nonfibrillated filawet-strength imparting resins or sizing materials such as anionic or soap sizes, rosin size, wax sizes, softening agents, impregnating agents, coating materials and the like.

Additional, and more complete descriptions of fiber 16 making procedures can be found in Us. Patents Nos. 2,558,735, 2,595,847, 2,613,195, 2,611,929 and 2,644,803,

in the same manner as set to the cellulosic paper bases.

THE REGENERATED CELLULOSE BASE Although the following discussion cipally to cellophane as a base, thls invention contemplates, as the base into which the photochromic material ally exists as a hydrophyllic cellulose, cellulose lacquer. The base film is essentially grease proof and can be made water vapor proof and even waterproof by adding various coating formulations thereto. The ultimate characteristics desired in the cellophane and the resultant alkali cellulose is pressed to remove excess liquor. The pressing reduces the weight of the cellulose down to approximately three times that of the pulp employed. The alkali cellulose is then shredded and to coagulate the viscose into a film and to regenerate the cellulose xanthate to cellulose. The film next proceeds through two tanks containing sulfuric acid and sodil it off and salt and acid is Washed from the cellulose film. The film is next removed to a dilute caustic bath wherein it is desulfurized and is then passed through two tanks containing warm water. A series of five tanks are then used to bleach and wash the film by removing the last traces of any remaining sulfur compounds.

It is at this point or any point further on in the cellophane making process that the photochromic material mentioned above may be incorporated. The qualification in regard to the addition of the photochromic materials is critical in the sense that they may not be added at any point in the cellophane making process whereat compounds or chemicals are present, or are to be added, which will interfere with, or negate, the color-changing property of the photochromic material or wash out or filter it out. Although it is not explicity mentioned hereinabove in regard to the paper bases, the same limitations as to interference by chemicals or compounds apply to papermaking procedures.

The last two tanks of the washing cycle in the cellophane process contain softening solutions such as aqueous ethylene glycol or aqueous glycerol. At this point in the washing cycle, water-soluble resin treatments may also be employed for coating the base film. The added resin is partially cured in the dryer and finally cured in the coating step. Sizes may also be added at this point in the system. The cellophane film is then passed through a dryer (where excess moisture is removed) and either wound into rolls or sent directly to coating machines.

The products of the present invention are not merely coatings of the solid photochromic materials on the paper bases or regenerated cellulose. The photochromic materials are actually uniformly dispersed or distributed throughout the mass of these substrates. They appear to be positioned in the fibers and in the interstices between interwoven fibers, and as such, they generally will not fall off when the papers or regenerated cellulose are being handled.

The amount of photochromic material added to the cellulosic paper, synthetic paper or regenerated cellulose according to the above defined procedures, is not critical. It is however, generally necessary to add enough photochromic additive so as to produce a visual change in color. That is to say, the cellulosic paper, synthetic paper or regenerated cellulose itself may have the ability to block out some of the ultraviolet light with which the photochromic component is to come into contact and therefore enough photochromic material must be present so as to allow for this reduced quantity of ultraviolet light with which it comes into contact and still produce a color change. We have generally found that amounts ranging from about 0.1% to about by weight, based on the dry weight of the cellulosic paper, synthetic paper or regenerated cellulose, are sufficient to obtain a satisfactory visible color change.

In summary, the process used for the production of the paper bases or regenerated cellulose does not form part of the present invention. The present invention is directed to the product produced by any paper or cellophane making process to which has been added the photochromic materials mentioned hereinabove at almost any point during the substrate-making process. The only governing feature of the photochromic material addition step is that the material should not be added during or prior to any step in the process at which a material, chemical, etc., is present which will react with the photochromic material and tend to reduce or neutralize its color changing ability, or to wash or filter it out. Therefore, the photochromic material should be added subsequent to any ste wherein reactive materials are present and any filtering or washing steps which will tend to remove the material.

It is possible to lengthen the life of the cellulosic paper, synthetic paper or regenerated cellulose compositions by incorporating various amounts of ultraviolet light absorbers into them or by coating them with a material containing an ultraviolet light absorber. When additives such as these are added, any conventional compound known to function as an ultraviolet light absorber may be employed. Examples of such compounds are the 2-hydroxy benzophenones, e.g., 2,4-di-hydroxy benzophenones; the 2(2-hydroxyphenyl)benzotriazoles, e.g., 2(2-hydroxy-4- methoxyphenyl)benzotriazole and the like. In this manner, the photochromic life of the photochromic material is lengthened by preventing an extraneous amount of ultraviolet light from coming into contact therewith. When absorbers of this type are added, amounts up to about 20% by weight based on the Weight of the substrate may be used.

The novel cellulosic paper, synthetic paper and regenerated cellulose products of the instant invention may be used for such items as memory devices, e.g., temporary photographic proofs, temporary data storage, temporary high speed direct recording paper for oscillographs', decorative materials, e.g., package wrappings, advertising articles; photocopy methods, e.g., production of permanent positive temporary negatives, temporary positives and the like.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

Example 1 To an aqueous slurry of wood pulp, containing 1% of a sulfite rosin size and 2% alum, is added 10%, by weight, of TiO activated by 0.2% Fe O based on the weight of the dry pulp. The pH of the slurry is adjusted to approximately 7.0 and the slurry is agitated for 10 minutes. The resultant suspension is formed into white hand sheets at 50 lb. basis weight (25 x 40"/ 500 ream) on a Nash hand sheet machine and dried at 240 F. The sheets produced are conditioned at 60 F. and 50% relative humidity for 24 hours. They are then contacted with ultraviolet light for 10 minutes. The white sheets turn a deep tan,

' Example 2 An aqueous suspension, of about 0.7% consistency, of bleached Northern Craft Pulp beaten to a Canadian Standard freeness of 450-500 ml. is formed. The pH of the system is adjusted to about 7.0 and 5%, based on the dry Weight of the fibers, of "H0 activated with 0.2% Fe O and 0.02% CuO, by weight, is added. The pH of the suspension is readjusted to 7.0 and the suspension is gently stirred for 5 minutes. The suspension is formed into white hand sheets in a manner set forth above in Example 1. The sheets turn a deep tan upon contact with ultraviolet light.

Example 3 An 18% aqueous caustic solution of wood pulp is produced by mixing the wood pulp with NaOH solution. The wood pulp is steeped for about 35 minutes and the resultant alkali cellulose is pressed, shredded and aged for 3 days. Carbon disulfide is added to the alkali cellulose in a large vat to produce sodium cellulose xanthate which is then dissolved in a caustic solution. The xanthate material is filtered, deaerated and ripened for 2 days. The resultant viscose is agitated and then extruded in the form of sheets into a coagulating and regenerating bath of sulfuric acid and sodium sulfate. The film is then washed with dilute sulfuric acid and sodium sulfate and then with dilute caustic. To this film is then added 15% by weight, based on the weight of the dry pulp, of TiO -12WO (produced by reacting one mole of TiO with 12 moles of W0 Warm water is then contacted with the film which is then washed with a softening solution comprising aqueous ethylene glycol. The film is then passed through a dryer and dried at F. The

Example 4 Wet spun, 3-denier polyacrylonitrile textile filaments are hand chopped to about A to 1" lengths and slurried with water to a 1% consistency. The resultant slurry is beaten in a one pound Valley laboratory beater with ten pounds on the 'bedplate arm.

To the resultant beaten slurry is then added 8% by weight, based on the dry weight of the polyacrylonitrile, of 2,3-diphenyl-1-inden0ne oxide. Samples of the suspension are then withdrawn and are formed into synthetic paper sheets on a Nash handsheet machine. The sheetsare dried on a drum dried at 240 F. for about 60 seconds.

Upon contact of the dry sheets with ultraviolet light, they turn from white to a deep pink.

.i.e. Examples to 38 followed Example 1 in photochromic material concentration. In Examples 39 to 60, the procedure set forth in Example 4 was followed in regard to the concentration employed of the solid state photochromic material.

We claim:

1. A water-laid web comprising water-fibrillated, ranplastic, acrylonitrile-containing, polymeric material, said web having umformly distributed throughout the interstices thereof, at least 0.1%, by weight, based on the weight of the web, of a photochromic material which is a solid at room temperature and which functions photochromically as a solid.

2. The base material of claim 1 wherein the photochromic material is T activated with Fe O TABLE I Ex. Base Activated W1th- Color Change Time Activation, See. M cellulosic Paper Tioz-IZMOOa l Wh to deep blue 60 6; Cellophane ZnO-6WO3 Falnt yellow to deep blue-green 30 T1O2+FeO Off-white to to 60 TlOz-l-CIaOa. 1, 800 TiOrl-CIIO- 120 TlOz+NiO 120 100 100 13 60 14 60 15 60 1 1, 200 17 1, 200 1g 2, 400 19 1, 400 20 2, 400 21 l, 500 22 1, 500 23 3,600 24- 203+V205 3, 600 25 ZnOz+CuO- 2, 700 25 ZnO +VzO5 d0 2, 700 27 SnO2+CuO. Ofi-white to deep tan 2,700 28 d ZrO+CuO Off-white to grey... 2, 700 2g Zr O1+N1O .ln do 2, 700 3g T m-W03" Fa nt yellow to blue-gree 60 TlO2-WOa {a}??? yelllpgttaldeep blue green 300 1 e 0 1g ue. 60 Z110 M003 lllvvfiifie to lbhfleslglu 300 1 e 0 1g ue. 60 M003 {White to blue 30o ZlOz-WOa Faint yellow to light blue-green Smo -M003 White to light blue 60 White to blue 300 SI102-WO3 Faint yellow to light blue-green 60 GeOz-WOa 1 do 60 White to light blu 60 to no. 300 Pale yellow to 60 do 120-180 Yellow to cram 120-180 ..do 1 120-180 Pale yellow to (1 yellow 120-180 Yellow to deep yellow 60 Yellow to red 300 White to pink 60 Colorless to orange 60 Pale yellow to deep yellow 300 Slight yellow to orange. 60 low to red 60 Pale yellow to deep yellow 60 Yellow to brown 120-180 Pale yellow to deep pink 120-180 Pale yellow to pink 120-180 Pink to red 120-180 White to yellow. 120-180 Colorless to orange l 120-180 White to yellow 120-180 Colorless to yellow 120-180 Colorless to deep blue 60 Colorless to blue 60 amounts as set fort Table I, above, discloses the eflectiveness of color change of cellulosic paper, synthetic paper and cello- I Examples 39 to 60 employed photochromic additives as designated by numbers 1 to 130 in the specification in h in Examlpe 1.

3. The base material of claim 1 wherein the photochromic material is 2,3-diphenyl-1-indenone oxide.

4. The base material of claim 1 wherein the photochromic material is piperonal m-tolylhydrazone.

5. The base material of claim 1 wherein the photospecific base in equal amounts, as disclosed in Example 1, chromic material is benzaldehyde m-tolylhydrazone.

6. The base material of claim 1 wherein the photochromic material is cinnamaldehyde 3,5-Xylylhydrazone.

7. The base material of claim 1 wherein the photochromic material is p-tolualdehyde Z-naphthylhydrazone.

8. The base material of claim 1 wherein the photochromic material is 3-(p-methoxybenzylideue)-2-pentanone thiosemicarbazone.

9. The base material of claim 1 wherein the photochromic material is 2-(2,4-dinitrobenzyl) pyridine.

10. A web according to claim 1 wherein said material is a fibrous, cellulosic material.

11. The cellulosic paper of claim 10 wherein the photochromic material is TiO activated with Fe O 12. A web according to claim 1 wherein said material is a fibrous, thermoplastic, polymeric material.

13. The synthetic paper of claim 12 wherein the photochromic material is TiO activated with Fe O References Cited by the Examiner UNITED STATES PATENTS 2,336,299 12/1943 Russell 96-88 2,710,274 6/1955 Kuehl 96-89 2,735,783 2/1956 Tamblyn et a1. 96-89 Wagner et a1. 96-89 Greig 96-1 Berman 96-89 Dorion et a1 96-90 X Montani 96-27 Cerreta et a1 96-90 Windsor 88-106 X FOREIGN PATENTS Canada.

OTHER REFERENCES Photographic Effects in Oxides, J.

ber 1955, pages 643-653.

Report 61-70, December 1961,

Contract #AF33(616)-6205, pages 332-351 of interest.

Day, Thermochromism, 1963, pages 65-80.

Chem. Reviews, vol. 63,

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,314,795

George Henry Dorion et al.

April 18, 1967 fied that error appears in the above numbered pat- It is hereby certi said Letters Patent should read as ent requiring correction and that the corrected below.

Column 8, line 54, for "chlorode" read chloride column 10, line 56, for "viscisity" read viscosity columns 13 and 14, in TABLE 1, third column, line 9 thereof,

for "TiO +Fe O read TiO +Fe O +NiO Signed and sealed this 14th day of November 1967.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Ir.

Commissioner of Patents Attesting Officer 

1. A WATER-LAID WEB COMPRISING WATER-FIBRILLATED, RANDOMLY INTERMINGLED, INTERLOCKED, FILAMENTS OF PAPER-MAKING LENGTH OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF A FIBROUS, CELLULOSIC MATERIAL AND A FIBROUS, THERMOPLASTIC, ACRYLONITRILE-CONTAINING, POLYMERIC MATERIAL, SAID WEB HAVING UNIFORMLY DISTRIBUTED THROUGHOUT THE INTERSTICES THEREOF, AT LEAST 0.1%, BY WEIGHT, BASED ON THE WEIGHT OF THE WEB, OF A PHOTOCHROMIC MATERIAL WHICH IS A SOLID AT ROOM TEMPERATURE AND WHICH FUNCTIONS PHOTOCHROMICALLY AS A SOLID. 